Edward Grainger has been summoned to West Berlin on a secret mission. He is told that he must discover the location of a missing research scientist and his team. The scientist just happens to be Edward's old friend George Tremayne, who had courted Eleanor Grainger for six months before she chose Edward.
Edward and Eleanor had just attended a talk given by George on the subject of the Voynich manuscript. After the talk, George told them that he had been reactivated and was being sent to study something that has been found.
Arriving in West Berlin, Edward is greeted by Captain Danby, who assumes Edward knows what is going on. Edward is taken to the house where George was working, and where a military team has been stationed. Edward is annoyed that Danby and the men think strange things are going on at the house, including the disappearance of all doors and windows. He learns from Danby that George is not missing; he's still in the house.
When they try to approach the house, a black something approaches and envelops Danby and two other men. Their faces have changed into George's face, and they speak with George's voice, telling Edward to enter the house and to keep the men away. George releases the men, and a door appears on the house.
When Edward enters, things look very strange inside the house. He finds one of George's research assistants fused into the flooring. He goes to the library, where he sees both George and a blue police box. George tells Edward that he was given a book of great power. He has strange symbols carved into his skin. He mentions that another man tried to stop him, and draws Edward's attention to the police box, where a grey haired man is fused into the wood. Edward says that the George that Eleanor knew wouldn't do this, George frees the man, who recognises Edward. He tells Edward that the book is called the Logos manuscript, and it is unbelievably ancient. It could rewrite the universe. They must stop George.
Edward is to distract George while the man will carve a "self-destruct" symbol onto George's skin that will stop him. Edward taunts George about Eleanor choosing him over George. The man is able to carve the symbol onto George's skin, and George disintegrates into ash while everything returns to normal.
When Edward goes to the men outside, he hears a strange noise behind him. When he turns around, the man and the police box are gone. He looks at the paper on which the man had copied the self-destruct symbol. It looks a lot like a question mark.
- The Doctor compares the errors in the Logos to the game of Chinese whispers.
- The Doctor mentions Sarah Jane and the Brigadier.
- The stories in Short Trips: The Centenarian revolve around Edward Grainger, a man who has met the Doctor more than a dozen times over the course of his life.
- Edward remembers seeing a blue police box at home in a cupboard (PROSE: Echoes) and in China. (PROSE: Falling from Xi'an)
- The Doctor is slowly dying from radiation sickness after entering the lair of the Great One. (TV: Planet of the Spiders)